Building structures containing external vapor permeable foam insulation

ABSTRACT

Attach a thermoplastic polymeric foam to multiple spaced apart structural support members of a structure wherein the foam has a resistance to water vapor permeability (mu) that is less than 50, a thermal conductivity that is less than 40 milliwatts per meter*Kelvin, a compressive strength that is greater than 80 kilopascals, and a density of 48 kilograms per cubic meter or less to provide insulation while also providing water vapor-permeability and structural durability to the structure.

CROSS REFERENCE STATEMENT

This application claims the benefit of U.S. Provisional Application No. 61/022,915, filed Jan. 23, 2008.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to vapor permeable foam, methods of using such foam for insulation in buildings and building structures containing such insulation.

2. Description of Related Art

There is a need to increase the level of thermal insulation in existing building structures without inducing vapor build-up and condensation within the building structure.

The European Energy saving directive of 2002 requires increasing insulation values of many building structures in European member states to lower energy consumption. However, it is critical to add insulation to these building structures without increasing the likelihood of vapor condensation within the building structures. Vapor condensation within a building structure can cause mold, mildew and decomposition of building structure components. Therefore, addition of any insulation to existing houses should have necessary vapor permeability.

It is further desirable for additional insulation to have a high compressive strength while simultaneously having a desired level of vapor permeability. Installation of additional insulation to existing building structures advantageously involves applying the insulation to the outside of the building structures, particularly roof structures so as to not disrupt the ability to occupy the building structure. Therefore, the insulation will desirably have enough permeability to avoid vapor condensation in the building structure while at the same time have sufficient compressive strength to support the weight of materials and workers applying the insulation without damage.

Typically, increasing the vapor permeability of a polymer foam decreases the foam's compressive strength. Similarly, increasing the vapor permeability can lead to a lower compressive strength and a higher thermal conductivity. Therefore, it has been unknown whether the objective of achieving an insulating foam that has a high enough compressive strength to support materials and workers without damage and that has a desirable thermal conductivity and water-vapor permeability is achievable with a thermoplastic foam.

United States patent application US2005/0055973 discloses an insulated structure with studs, inner and outer sheathing and an insulation component between the studs. The outer sheathing can be a foam. However, the reference describes no properties of the foam. The insulation between the studs can also be a foam and that is, preferably, highly vapor permeable with a vapor permeance of between about 7 and 13 perms 565 ng/(Pa*s*m²) for a five inch (127 mm) thick section. Such a vapor permeability corresponds to a permeance relative to air of about 2.1-3.8 mu.

U.S. Pat. No. 5,996,289 and U.S. Pat. No. 6,145,255 disclose soffit ventilation systems that can include an open cell foam in order to allow for ventilation while preventing egress of insects into an attic space. It is unclear whether the foam of these patents is rigid or flexible. Moreover, a foam in such a soffit applications desirably would have high thermal conductivity (low insulating value) to prevent trapping of heat in an attic space.

Great Britain patent (GB) 1396182 and GB 1396582 disclose open cell foam structures suitable for applications requiring vapor transmission. The foams are prepared from a solution by dissolving a polymer into a solvent. GB 1396182 achieves an example having a 95% void volume (and a density of approximately 50 kilograms per cubic meter (kg/m³) assuming the polymer composition has a specific gravity of approximately one gram per cubic centimeter) that is “tough”. However, another example having 98% void volume (approximately 20 kg/m³ density) is “soft and compressible”. Therefore, it is clear that decreasing the density of these foams reduces their compressive strength. Hence, it is unclear what compressive strength a foam having a density of less than 48 kg/m³ will have. Moreover, there is no discussion of thermal conductivity or a measure of vapor permeability for these foams.

Australian patent application AU2006203389 discloses a perforated foam sheet suitable for insulation where moisture permeability is desirable. The reference discloses several embodiments of a foam that differ in cell size and, likely, other properties. One type of foam has a cell structure whose cells are cylindrical in shape with a diameter between about eight millimeters and 25 millimeters. A foam with such a large cell size will have poor thermal insulating properties due to high convection of heat through the cells. The other type of foam in this reference is a closed-cell foam having an average cell size of less than 0.1 millimeters and that is flexible and capable of rolling up.

BRIEF SUMMARY OF THE INVENTION

The present invention is the result of surprisingly discovering a foam that is especially well suited for insulating a building structure, particularly retro-insulating a building structure, because the foam concomitantly has a vapor permeability sufficiently high to allow water vapor to escape the building structure while also having a low enough thermal conductivity to serve as a thermal insulator and a compressive strength sufficient to support materials and workers during installation.

In a first aspect, the present invention is a building structure comprising: (a) multiple support members spaced apart from one another so that two neighboring support members have a space between them and each support member having opposing inside and outside surfaces; and (b) a thermoplastic polymer foam spanning the space between two neighboring support members and attached to the outside surface of two or more of the support members; wherein, the thermoplastic polymer foam: (i) has a resistance to water vapor permeability value that is less than 50 according to EN 12086; (ii) a thermal conductivity that is less than 40 milliWatts per meter*Kelvin as measured according to EN12667; (iii) a compressive strength greater than 80 kilopascals as measured according to EN 826; and (iv) a density of 48 kilograms per cubic meter or less according to EN 1602.

Embodiments of the first aspect of the present invention may have any one or any combination of more than one of the following characteristics: the thermoplastic polymer foam has a continuous polymer phase comprising an alkenyl aromatic polymer; the building structure is free of a vapor barrier component having a water vapor permeability value higher than 50 as measured according to EN12086 and that extends across two or more support members spanned by the thermoplastic polymer foam; the thermoplastic polymer foam has a resistance to water vapor permeability of 10 or more; the thermoplastic polymer foam is further characterized by having a density of 24-48 kilograms per cubic meter according to ISO 845-95; the thermoplastic polymer foam is further characterized by having an open cell content of 40% or more and 100% or less according to ASTM D2856; the thermoplastic polymer foam is further characterized by having a thickness of 50 millimeters or more; the building structure is one or more structure selected from a group consisting of roof structures and wall structures; the building structure is a timber frame wall structure; the building structure is a pitched roof structure; and adjacent support members define a cavity between them and the building structure further comprises insulation residing in more than one cavity between support members.

In a second aspect, the present invention is a method for insulating a building structure comprising the following steps: (a) providing multiple support members spaced apart from one another so that two neighboring support members have a space between them and each having opposing inside and outside surfaces; (b) providing a thermoplastic polymer foam that has a resistance to water vapor permeability that is less than 50 as measured according to EN12086, a thermal conductivity that is less than 40 milliWatts per meter*Kelvin as measured according to EN 12667, a compressive strength that is greater than 80 kilopascals as measured according to EN 826, and a density of 48 kilograms per cubic meter or less according to EN 1602; and (c) attaching the thermoplastic polymer foam to two or more of the support members such that the foam spans the space between two neighboring support members.

Embodiments of the second aspect can have any one or any combination of more than one of the following characteristics: the thermoplastic polymer foam has a continuous polymer phase comprising an alkenyl aromatic polymer; the thermoplastic polymer foam has a resistance to water vapor permeability value of 10 or more; the thermoplastic polymer foam is further characterized by having a density of 24-48 kilograms per cubic meter according to EN 1602; the thermoplastic polymer foam is further characterized by having an open cell content of 40% or more and 100% or less according to ASTM D2856; the thermoplastic polymer foam is further characterized by having a thickness of 50 millimeters or more; the building structure is one or more structure selected from a group consisting of roof structures and wall structures; the building structure is a timber frame wall structure; and the building structure is a pitched roof structure.

The present invention has particular utility in insulating building structures by either building new or by adding insulation to existing structures in order to meet higher thermal insulting requirements and demands while avoiding hazards associated with retaining water within a building structure.

DETAILED DESCRIPTION OF THE INVENTION Terms

“Multiple” means two or more.

“ASTM” refers to American Society for Testing and Materials. ASTM test methods refer to the test method of the year noted by the hyphenated suffix after the test method number or the most recent test method prior to filing this application.

“Internal” and “inside” refer to a side that is most proximate to a space defined by (hence, within) a building structure. In a home structure, the “inside” or “internal” side is the side facing the dwelling side of the structure that is typically heated in cold portions of the year.

“External” or “outside” refers to a side that is opposite the internal or inside and that is most remote from a space defined by a building structure. The external or outside portion of a building element is most proximate to the natural environment in which the building structure is built.

“Span” means to extend all the way across. To span a space between two support members means to extend from one support member across the space to the other support member.

Resistance to water vapor permeability is in adimensional units of “mu” or “μ”. Each unit of mu is equal to the resistance of water vapor permeability through standing air. Determine mu for a given material according to the general procedure of EN 12086-95.

Foam Insulation

Thermoplastic polymer foam for use in the present invention (the “present thermoplastic polymer foam”) can be any type of foam, including expanded polymer bead foam or extruded polymer foam.

In an expandable polymer bead process prepare a foamable composition by incorporating a blowing agent into granules of polymer composition (for example, imbibing granules of polymer composition with a blowing agent under pressure). Subsequently, expand the granules in a mold to obtain a foam composition comprising a multitude of expanded foam beads (granules) that adhere to one another to form a “bead foam”. The granules can experience some level of foaming prior to expansion within a mold to form a bead foam. Alternatively, expand the beads apart from a mold and then fuse them together thermally or with an adhesive within a mold. Bead foam has a characteristic continuous network of polymer skin corresponding to the surface of each individual bead extending throughout the foam.

Extrusion processes are most desirable. Foams made from expandable foam bead processes have a network of polymer skins (bead skins) that define and enclose groups of cells within the foam. Such skins are residual skins from each foam bead that expanded to form the foam. The bead skins coalesce together to form a foam structure comprising multiple expanded foam beads. Bead foams tend to be more friable than extruded foam because they can fracture along the bead skin network. Moreover, the bead skin network provides a continuous thermal short from any one side of the foam to an opposing side, which is undesirable in a thermal insulating material. Extruded foams are continuous, seamless structures free from having, for example, the network of bead skins characteristic of expanded bead foam. An extruded foam can be a “strand foam”. That is, the extruded foam may comprise multiple extruded strands of foam that are fused together. A strand foam has a polymer network skin extending along the extrusion direction of the foam but not in a direction perpendicular to the extrusion direction. Hence, a strand foam is free of a continuous polymer skin (which can cause a thermal short) extending all the way through the strand foam in a direction perpendicular to the extrusion direction as there is in an expanded bead foam. Nonetheless, it is most desirable that the extruded foam be a continuous, seamless structure as opposed to a bead foam structure or other composition comprising multiple individual foams that are assembled together in order to maximize structural integrity and thermal insulating capability.

In an extrusion process prepare a foamable composition by mixing a thermoplastic polymer composition and, optionally, additives in an extruder at a temperature sufficiently high to soften the polymer composition, and then mixing in a blowing agent at an addition pressure sufficient to preclude appreciable expansion of the polymer composition. It is acceptable to either feed additives directly into the extruder or to pre-mix additives with a polymer prior to addition to an extruder (i.e., compound it or create a masterbatch). It is desirable to then cool the foamable composition to a foaming temperature and then expel the foamable composition through a die into an environment of lower pressure than the addition pressure. As the foamable composition enters the environment of lower pressure it expands into a polymer foam.

Blowing agents are typically present in a combined concentration of 0.001 mole per 100 grams of polymer to 0.5 mole per 100 gram of polymer. Suitable blowing agents for use in an extrusion foaming process include one or more of the following: inorganic gases such as carbon dioxide, argon, nitrogen, and air; organic blowing agents such as water, aliphatic and cyclic hydrocarbons having from one to nine carbons including methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane, neopentane, cyclobutane, and cyclopentane; fully and partially halogenated aliphatic hydrocarbons having from one to five carbons, preferably that are chlorine-free (e.g., difluoromethane (HFC-32), perfluoromethane, ethyl fluoride (HFC-161), 1,1,-difluoroethane (HFC-152a), 1,1,1-trifluoroethane (HFC-143a), 1,1,2,2-tetrafluoroethane (HFC-134), 1,1,1,2 tetrafluoroethane (HFC-134a), pentafluoroethane (HFC-125), perfluoroethane, 2,2-difluoropropane (HFC-272fb), 1,1,1-trifluoropropane (HFC-263fb), 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), 1,1,1,3,3-pentafluoropropane (HFC-245fa), and 1,1,1,3,3-pentafluorobutane (HFC-365mfc)); aliphatic alcohols having from one to five carbons such as methanol, ethanol, n-propanol, and isopropanol; carbonyl containing compounds such as acetone, 2-butanone, and acetaldehyde; ether containing compounds such as dimethyl ether, diethyl ether, methyl ethyl ether; carboxylate compounds such as methyl formate, methyl acetate, ethyl acetate; carboxylic acid and chemical blowing agents such as azodicarbonamide, azodiisobutyronitrile, benzenesulfo-hydrazide, 4,4-oxybenzene sulfonyl semi-carbazide, p-toluene sulfonyl semi-carbazide, barium azodicarboxylate, N,N′-dimethyl-N,N′-dinitrosoterephthalamide, trihydrazino triazine and sodium bicarbonate.

The polymer foam may contain any individual or combination of the following additives: infrared attenuating agents (for example, carbon black, graphite, metal flake, titanium dioxide); clays such as natural absorbent clays (for example, kaolinite and montmorillonite) and synthetic clays; nucleating agents (for example, talc and magnesium silicate); flame retardants (for example, brominated flame retardants such as hexabromocyclododecane, phosphorous flame retardants such as triphenylphosphate, and flame retardant packages that may including synergists such as, or example, dicumyl and polycumyl); lubricants (for example, calcium stearate and barium stearate); and acid scavengers (for example, magnesium oxide and tetrasodium pyrophosphate). A preferred flame retardant package includes a combination of hexahalocyclododecane (for example, hexabromocyclododecane) and tetrabromobisphenol A bis (2,3-dibromopropyl ether.

The polymer foam has a thermal conductivity of 40 milliWatts per meter*Kelvin (mW/m*K) or less, preferably, 35 mW/m*K or less. Lower thermal conductivity values are desirable to maximize thermal insulating capability for the foam. The lower the thermal conductivity of a foam, the less thickness is necessary to achieve a given measure of thermal insulation. Measure thermal conductivity at 10° C. mean temperature according to test method EN 8301-91.

Additionally, the polymer foam has a compressive strength greater than 80 kilopascals (kPa), preferably 120 kPa or more, more preferably 170 kPa or more, still more preferably 200 kPa or more. Measure compressive strength according to ASTM D-1621-04. Higher compressive strengths are desirable in an insulating foam over lower compressive strengths in order to provide durability during handling, installation and use. The compressive strength of present thermoplastic polymer foams renders them rigid foams. In contrast, flexible foams are not suitable alternatives to the thermoplastic polymer foams for use in the present invention. Flexible foams necessarily have an undesirably low compressive strength in order to flex and, therefore, cannot sustain loads in a roofing application without deformation or inhibit racking in walls like the present thermoplastic polymer foam.

The polymer foams of the present invention have properties that surprisingly balance conflicting effects of achieving a low thermal conductivity and high compressive strength (typically achieved using a closed-cell foam with low permeability) with achieving vapor permeability through the foam that is high enough provide for more water vapor to permeate through the foam than is retained from permeating through the foam.

Polymer foams of the present invention have a resistance to water vapor permeability (“mu” or “μ”) of 50 or less, preferably 40 or less more preferably 30 or less as measured according to EN 12086-95. The foam can have a mu value of 20 or less. Higher mu values correspond to foams having lower water vapor permeability. When the mu value is greater than 50 the polymer foam generally will have too low of a water vapor transmission capability and water condensate will likely build up proximate to a building structure on which the foam resides. At the same time, it is desirable not to have too low of a mu value or the thermal insulating value of the foam becomes too low to be of value and, typically, the compressive strength decreases. Hence, it is desirable for the foam to have a mu value of 10 or more.

In order to achieve the desired water vapor permeability, the polymer foam desirably has an open cell content of 40% or more, preferably 50% or more, more preferably 60% or more. Measure open cell content according to American Society for Testing and Materials (ASTM) method D2856. Increasing open cell content increases water vapor permeability. However, too high of an open cell content can detrimentally raise thermal conductivity and lower compressive strength. Typically the polymer foam has an open cell content of 100% or less, more typically 80% or less.

The polymer foam can have an open cell content below 40%, even below 30% or 20% or even 10%. The polymer foam can have an open cell content of 0%. However, if the open cell content is too low to achieve the necessary mu value then the foam must undergo perforation so as to provide perforations though the foam to increase water vapor permeability. Desirably, the thermoplastic foams are not perforated but rather have an inherent open cell structure (that is, an open cell structure resulting from expansion of the cells during manufacture). Inherently open cell foams have a torturous path through the cell structures from one side to the other of the foam without a linear paths through from one side to the other. In contrast, perforated foams have linear paths through the foam from one side to the other where perforating needles penetrate through the foam.

If the foam contains perforations, the perforation are preferably 2 millimeters or less in diameter in order to minimize detrimental effect on (that is, increase in) thermal conductivity. When the perforations are 2 millimeters or less in diameter, airflow does not occur extensively enough to effect thermal conductivity. Nonetheless, water vapor can still permeate effectively through the perforations.

The polymer foam has a density of 64 kilograms per cubic meter (kg/m³) or less, preferably 40 kg/m³ or less, more preferably 30 kg/m³ or less. Measure foam density according to ISO 845-95. Lower density foams are desirable because they contribute less weight to building structures, and weight can be a particular concern for roof structures. Low density foams are also desirable for easier handling and shipping. Typically, the polymer foam has a density of 20 kg/m³ or more in order to ensure sufficient compressive strength and durability.

The foam desirably has a thickness of at least 15 millimeters, preferably at least 30 millimeters and more preferably at least 50 millimeters in order to provide optimal insulating value and also provide structural integrity to the building structure (for example, to provide stability against racking in timber frame structures).

The thermoplastic polymer foam has a continuous polymer phase that desirably comprises or consists of one or more than one alkenyl aromatic polymer. The continuous polymer phase includes all polymers present in the thermoplastic foam at a concentration greater than 20 wt % based on the thermoplastic polymer foam weight. Polymers present at a concentration less than 20 wt % of the thermoplastic polymer foam are considered additives in the continuous polymer phase as opposed to part of the continuous polymer phase. For example, a continuous polymer phase may “consist of” styrenic polymers even though there are non-styrenic polymer additives present at a concentration less than 20 wt % of the thermoplastic polymer foam weight.

An alkenyl aromatic polymer contains polymerized alkenyl aromatic monomer units and includes homopolymers and copolymers containing alkenyl aromatic monomer units (i.e., made from monomers that include alkenyl aromatic monomers). Polystyrene (PS) based polymers (that is, PS homopolymer and copolymers) are one particularly preferred class of alkenyl aromatic polymers. Particularly desirable PS polymers are PS homopolymer and PS copolymer with acrylonitrile (styrene-acrylonitrile copolymer (SAN)).

Typically, the present thermoplastic polymer foam is free of a continuous polymer phase that consists of polyethylene (PE), polypropylene (PP) or a combination of PE and PP. The modulus of most PE and PP polymers is too low to provide a thermoplastic polymer foam having a combination of vapor permeability, compressive strength and thermal conductivity of the present thermoplastic polymer foam.

The present thermoplastic foam typically has an average cell size that is greater than 50 microns, preferably greater than 70 microns, and is more preferably 100 microns or larger, still more preferably 200 microns or larger. The average cell size is desirably 2000 microns or smaller, preferably 1000 microns or smaller, more preferably 500 microns or smaller. When the average cell size is less than 50 microns, thermal conductivity and density tend to increase undesirably due a large amount of polymer in a given through the foam's cross section. When the cell size exceeds 2000 microns, thermal conductivity tends to begin to increase due to convention through the foam. Measure average cell size according to American Society for Testing and Materials method D-3576.

Insulated Building Structure

The present thermoplastic polymer foam is useful for insulating building structures. In particular, the thermoplastic polymer foam offers advantages over other insulating foam when applied to the outside of a building where thermal insulation needs to be permeable to water vapor in order to allow vapor to escape to the atmosphere from between the insulating foam and building structure. Without being permeable to water vapor, insulating foam applied to the outside to prevent water vapor build-up and condensation between the insulating foam and building structure.

Typically, it is desirably to have water vapor barriers between the inside of a structure and the structural elements/insulation to prevent water vapor from getting trapped in the structural elements/insulation. Water-vapor build up and condensation can be particularly problematic when there is no such water vapor barrier because humidity from inside the structure and enter the structural elements and insulation. Even more problematic is if the water-vapor cannot escape from the structural elements/insulation. The high vapor permeability of the present thermoplastic polymeric foam is particularly useful for applying to structure from the outside because it allows water vapor to escape from the structural elements/insulation within the structure. Therefore the present thermoplastic polymeric foam is especially suited for modifying existing structures to increase insulation (that is, “retro-insulating” existing structures).

In general, the thermoplastic foam can be applied onto any building structure in any manner. However, it is particularly useful for spanning two or more (“multiple”) support members of a building structure that are spaced apart from one another. For example, roof rafters and wall joists are examples of support members of a building structure. The high compressive strength of the present thermoplastic foams make the present thermoplastic foams well suited for supporting loads even between support members without breaking. Generally, an insulating thermoplastic foam having a high vapor permeability like the present foam does not have sufficient compressive strength to support loads between support members. Hence, insulated building structures comprising multiple support members spaced apart from one another such that two neighboring support members have a space between them and each support member having opposing inside and outside surfaces with the present thermoplastic foam spanning the space between two neighboring support members and attached to the outside surface of two or more of the support members is unique and offers a desirable structure having a combination of high insulating ability, high compressive strength and vapor permeability.

In one embodiment, the thermoplastic foam is useful for insulating, particularly retro-insulating, pitched roofs on building structures such as houses by attaching to outside surfaces of roof structural elements. Roof structures typically comprise spaced apart structural elements such as rafters or furring strips spanning rafters. These elements have opposing inside surfaces and outside surfaces with the inside surfaces most proximate to the attic or inside of the building structure. In many older buildings, ventilation is sufficient through the roof and any insulation between the rafters (for example, mineral wool) to allow water vapor to pass through from the inside to the outside of the roof structure. Other foam insulation, such as close-celled polymer foam and insulation having vapor impermeable facers are not suitable for such an application because they would trap moisture within the attic. Even in newer buildings, a vapor barrier is typically present proximate to the inside of the structural elements so applying an insulation component on the outside that is impermeable to water vapor would serve to undesirably trap moisture between the insulation and building structural elements.

Pitched roof structures of the present invention may comprise, in addition to the structural elements and present thermoplastic foam, at least one of the following additional elements: a breathable membrane and finishing elements (such as shingles, battens and tiles) with the thermoplastic foam between the additional element or elements and the structural elements. The additional element or elements are desirably attached to the thermoplastic foam, which is attached to the structural element such that the thermoplastic foam is between the additional element(s) and the structural elements.

The present thermoplastic polymer foam is ideally suited for insulating wall structures from the outside, which is particularly desirable in retro-insulating building structures. The vapor permeability of the present thermoplastic polymer foam allows moisture to escape. Moreover, the compressive strength of the present thermoplastic polymer foam strengthens the wall structure against deformation by, for example, racking.

In any of the insulated structure embodiments of the present invention, additional insulation may be present in a cavity defined by neighboring structural elements. For example, inter-joist or inter-rafter cavities may contain mineral wool or fiberglass or other fibrous insulation while the present thermoplastic polymer foam spans the outside surface of the joists, rafters, or other structural elements defining the cavity.

Method of Insulating a Building Structure

Prepare building structures of the present invent by providing multiple support members spaced apart from one another so to form a space between them and each having opposing inside and outside surfaces, providing a present thermoplastic polymer foam and attaching the thermoplastic polymer foam to two or more of the support members such that the foam spans the space between two support members. A single foam may span the space between more than one pair of neighboring support members.

The support members can be of any composition, with common materials being wood (for example, lumber joists and studs) and metal (for example, metal joists and studs). Attach the present thermoplastic foam to the support members by any means including screws, nails, adhesives or any combination thereof. The present thermoplastic foam may directly contact the support member or may be separated from the support member by anything that has a vapor permeability no less than that of the present thermoplastic polymer foam.

EXAMPLES

The following examples serve to further illustrate embodiments of the present invention.

Preparation of a Thermoplastic Polymer Foam for Use in the Present Invention Foam Sample 1: SAN Foam

Prepare a foamable composition by feeding a blend of SAN copolymer (80% of Mw=118,000 with Mw/Mn=2.3 and 20% of Mw=145,000 and Mw/Mn=2.2), 0.22 weight-parts per hundred weight parts copolymer (pph) barium stearate, 0.25 pph polyethylene, 0.20 pph copper blue phthalocyanine, 0.12 pph tetrasodium pyrophosphate and 2 pph of hexabromocyclododecane into an extruder at a temperature of approximately 200° C. to form a melt. Extrude the melt into a mixer and inject into the melt 9.8 weight parts per hundred weight parts of SAN copolymer of a blowing agent composition consisting of 19 wt % carbon dioxide, 67 wt % tetrafluoroethane (R134a) and 14 wt % isobutane (iC₄) into the melt at 136 bar pressure and mix to form the foamable composition.

Cool the foamable composition to a temperature of about 130° C. and extrude through a slit die into atmospheric pressure whereupon the foamable composition expands into a polymeric foam (Sample 1). Table 1 identifies properties of Sample 1.

Sample 2: Polystyrene Foam

Table 1 also identifies properties for Sample 2, a polystyrene foam.

TABLE 1 Property Units Sample 1 Sample 2 Thickness mm 17 60 Density kg/m³ 33.5 32.7 Cell Size mm 0.12 0.38 Compressive Strength kPa 399 372 Dimensional Stability % 0.8 1.8 Open Cell % 34.7 84.4 Thermal conductivity mW/m * K. 34.6 37.3 Water Vapor Permeability ng/m * s * Pa 4.2 9.75 Resistance to Water Vapor mu (μ) 47 21 Permeability

Determine foam density according to ISO 845-95, cell size according to ASTM D-3576, compressive strength according to ASTM D-1621-04, foam dimensional stability according to DLT(1)5 (WD)-EN 1605, open cell content according to ASTM method D2856, thermal conductivity at 10° C. mean temperature according to EN 8301-91 and resistance to water vapor permeability according to EN 12086-95.

Example of a Roof Structure

It is desirable to be able to increase insulation of a pitched roof of a building structure without disturbing the occupancy within the building structure. Hence, it is desirable to increase insulation from the outside of the building structure, but also desirable not to create a water vapor barrier on the outside of the structure in the process for fear of condensing water vapor within the building structure. This example provides an illustration of one method of installing insulation to a roof structure comprising multiple rafters that optionally contain insulation between the rafters.

In this example, provide a roofing structure having spaced apart rafters, optionally containing fiberglass or mineral wool insulation between the rafters, optionally containing a batten structure affixed on the inside of the roof structure that provides a level surface for plaster or plaster boards to be affixed as the substructure for the inside walls of the structure. Battens are also affixed to the outer surface of the structure to which roofing material such as tiles or shingles are attached.

In this exemplary embodiment, increase the insulation of this roofing structure by first removing the roofing material (for example, tiles or shingles) and battens on the outside of the rafters. Affix by means of an adhesive or mechanical fastener (for example, nails or screws) to multiple rafters a styrene-based polymer foam board (for example, either of Sample 1 or Sample 2) that has a resistance to water vapor permeability that is less than 50 as measured according to EN12086, a thermal conductivity that is less than 40 milliWatts per meter*Kelvin a measured according to EN 12667, a compressive strength that is greater than 80 kilopascals as measured according to EN 826 and a density of 48 kilograms per cubic meter or less according to EN 1602 so that the polymer foam board entirely spans two or more rafters. Ideally, repeat this process so that all of the rafters are covered with polymeric foam and there is no spacing between polymeric foam boards. Desirably, though not necessarily, apply a water vapor permeable membrane over the polymeric foam boards. Desirably, apply counter battens over the permeable membrane or polymeric foam boards. Desirably, apply battens over the counter battens if present; or if not present over, the permeable membrane, if present; or if neither the counter battens nor water vapor permeable membranes are present, over the polymeric foam. Apply roofing materials such as tiles, shingles or metal sheet over the battens. 

1. A building structure comprising: a. multiple support members spaced apart from one another so that two neighboring support members have a space between them and each support member having opposing inside and outside surfaces; and b. an extruded thermoplastic polymer foam spanning the space between two neighboring support members and attached to the outside surface of two or more of the support members; wherein, the thermoplastic polymer foam: (i) has a resistance to water vapor permeability that is less than 50 according to EN 12086; (ii) a thermal conductivity that is less than 40 milliWatts per meter*Kelvin as measured according to EN12667; (iii) a compressive strength greater than 80 kilopascals as measured according to EN 826; and (iv) a density of 48 kilograms per cubic meter or less according to EN
 1602. 2. The building structure of claim 1, wherein the thermoplastic polymer foam has a continuous polymer phase comprising an alkenyl aromatic polymer.
 3. The building structure of claim 1, wherein the building structure is free of a vapor barrier component having a resistance to water vapor permeability higher than 50 as measured according to EN12086 and that extends across two or more support members spanned by the thermoplastic polymer foam.
 4. The building structure of claim 1, wherein the thermoplastic polymer foam has a resistance to water vapor permeability of 10 or more.
 5. The building structure of claim 1, wherein the thermoplastic polymer foam is further characterized by having a density of 24-48 kilograms per cubic meter according to ISO 845-95.
 6. The building structure of claim 1, wherein the thermoplastic polymer foam is further characterized by having an open cell content of 40% or more and 100% or less according to ASTM D2856.
 7. The building structure of claim 1, wherein the thermoplastic polymer foam is further characterized by having a thickness of 50 millimeters or more.
 8. The building structure of claim 1, wherein the building structure is one or more structure selected from a group consisting of roof structures and wall structures.
 9. The building structure of claim 1, wherein the building structure is a timber frame wall structure.
 10. The building structure of claim 1, wherein the building structure is a pitched roof structure.
 11. The building structure of claim 1, wherein adjacent support members define a cavity between them and the building structure further comprises insulation residing in more than one cavity between support members.
 12. A method for insulating a building structure comprising the following steps: a. providing multiple support members spaced apart from one another so that two neighboring support members have a space between them and each having opposing inside and outside surfaces; b. providing an extruded thermoplastic polymer foam that has a resistance to water vapor permeability that is less than 50 as measured according to EN12086, a thermal conductivity that is less than 40 milliWatts per meter*Kelvin as measured according to EN 12667, a compressive strength that is greater than 80 kilopascals as measured according to EN 826, and a density of 48 kilograms per cubic meter or less according to EN 1602; and c. attaching the thermoplastic polymer foam to two or more of the support members such that the foam spans the space between two neighboring support members.
 13. The method of claim 12, wherein the thermoplastic polymer foam has a continuous polymer phase comprising an alkenyl aromatic polymer.
 14. The method of claim 12, wherein the thermoplastic polymer foam has a resistance to water vapor permeability of 10 or more.
 15. The method of claim 12, wherein the thermoplastic polymer foam is further characterized by having a density of 24-48 kilograms per cubic meter according to EN
 1602. 16. The method of claim 12, wherein the thermoplastic polymer foam is further characterized by having an open cell content of 40% or more and 100% or less according to ASTM D2856.
 17. The method of claim 12, wherein the thermoplastic polymer foam is further characterized by having a thickness of 50 millimeters or more.
 18. The method of claim 12, wherein the building structure is one or more structure selected from a group consisting of roof structures and wall structures.
 19. The method of claim 12, wherein the building structure is a timber frame wall structure.
 20. The method of claim 12, wherein the building structure is a pitched roof structure. 